Typically, inking units for offset printing machines include an ink-fountain roller dipping into an ink fountain, an ink-lifter roller, and a downstream ink take-off roller associated with the inking unit roller train. The ink-fountain roller may be independently driven. Ink is first collected on the ink fountain roller, then transferred by contact with the ink lifter roller, then transferred by contact of the ink lifter roller with the ink take-off roller for delivery to the roller train of the inking unit. Such inking units generally also include some means for cleaning of the inking unit.
An inking unit of this type is known from German Auslegeschrift 2,316,635, in which the cleaning fluid is applied to a first inking roller and the mixture of ink and cleaning fluid is wiped off of a second inking roller. A manual operation is performed to move the various rollers into engagement for cleaning purposes. DE 3,606,006 A1 discloses a device for cleaning an inking unit, in which the cleaning fluid is applied in dependence on the ink-layer thickness on the rollers/cylinders, with a string length being taken into account. At least two feeds for the cleaning fluid are provided for the primary and the secondary string of the inking unit.
An inking unit for offset printing machines, which can be operated convertibly as an overshot ink fountain or as an undershot ink fountain, is known from DE 2,703,424 B1. In the undershot mode, the ink lifter roller is pivoted between the ink fountain roller and the associated ink take-off roller of the roller train. In conversion to the overshot mode, the ink take-off roller is coupled to the ink fountain roller and the ink lifter roller serves as a rider roller. The ink take-off roller can be transferred into both positions via an eccentric mounting. The ink-fountain roller in this device cannot be cleaned together with the remaining roller train and therefore has to be cleaned manually by the operator.